US8731037B2 - Receiver, integrated circuit, receiving method, and program - Google Patents

Receiver, integrated circuit, receiving method, and program Download PDF

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US8731037B2
US8731037B2 US13/809,921 US201213809921A US8731037B2 US 8731037 B2 US8731037 B2 US 8731037B2 US 201213809921 A US201213809921 A US 201213809921A US 8731037 B2 US8731037 B2 US 8731037B2
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interference wave
interference
ofdm symbol
power
estimation unit
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US20130114659A1 (en
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Mariko Murakami
Yoshinobu Matsumura
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Panasonic Corp
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Panasonic Corp
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00Arrangements for monitoring or testing data switching networks
    • H04L43/08Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0823Errors, e.g. transmission errors
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2647Arrangements specific to the receiver only
    • H04L27/2655Synchronisation arrangements
    • H04L27/2689Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2691Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation involving interference determination or cancellation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04JMULTIPLEX COMMUNICATION
    • H04J11/00Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J11/0023Interference mitigation or co-ordination
    • H04J11/0026Interference mitigation or co-ordination of multi-user interference
    • H04J11/0036Interference mitigation or co-ordination of multi-user interference at the receiver
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/004Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045Arrangements at the receiver end
    • H04L1/0047Decoding adapted to other signal detection operation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048Allocation of pilot signals, i.e. of signals known to the receiver
    • H04L5/005Allocation of pilot signals, i.e. of signals known to the receiver of common pilots, i.e. pilots destined for multiple users or terminals
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00Diagnosis, testing or measuring for television systems or their details
    • H04N17/004Diagnosis, testing or measuring for television systems or their details for digital television systems
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006Arrangements for removing intersymbol interference
    • H04L2025/0335Arrangements for removing intersymbol interference characterised by the type of transmission
    • H04L2025/03375Passband transmission
    • H04L2025/03414Multicarrier
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202Channel estimation
    • H04L25/022Channel estimation of frequency response
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202Channel estimation
    • H04L25/0224Channel estimation using sounding signals
    • H04L25/0228Channel estimation using sounding signals with direct estimation from sounding signals
    • H04L25/023Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
    • H04L25/0232Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2647Arrangements specific to the receiver only
    • H04L27/2655Synchronisation arrangements
    • H04L27/2662Symbol synchronisation

Definitions

  • the present invention relates to a receiver, an integrated circuit, a receiving method, and a program, and in particular, to a receiver, an integrated circuit, a receiving method, and a program that are provided with a demodulator for demodulating a modulation wave modulated according to orthogonal frequency division multiplexing (OFDM).
  • OFDM orthogonal frequency division multiplexing
  • orthogonal frequency division multiplexing In various types of current digital communication such as terrestrial digital broadcasting, IEEE802.11a and the like, orthogonal frequency division multiplexing (OFDM) has been widely adopted as a transmission method.
  • OFDM orthogonal frequency division multiplexing
  • An exemplary OFDM receiver generates reliability information by using calculated noise power, and utilizes the reliability information to enable high-accuracy error correction using an LDPC (Low Density Parity Check) code (for example, PTL 1).
  • LDPC Low Density Parity Check
  • PTL 1 Low Density Parity Check 1
  • average noise power in a symbol direction is compared with noise power in each symbol, and in the case where the noise power in each symbol exceeds a predetermined threshold, it is determined that impulse interference exists, and a value of the noise power in each symbol is used to generate the reliability information.
  • the impulse interference means an irregular and random interference signal. Since impulse noise occurs in an impulse manner from, for example, power-ON/OFF of household electrical appliances, lighting equipment or automobile ignition, the noise power locally increases in the symbol in which the impulse noise exists.
  • PTL 2 There is a method of estimating the noise power existing in each symbol, which is necessary for estimating the reliability information (for example, PTL 2).
  • PTL 2 describes that, in ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) as Japanese terrestrial digital broadcasting, either or both TMCC (Transmission Multiplexing Configuration Control) signals and AC (Auxiliary Channel) signals, which are continuously inserted into a predetermined subcarrier in a time direction are used to estimate the reception quality.
  • TMCC Transmission Multiplexing Configuration Control
  • AC Advanced Channel
  • the conventional noise power calculation methods disadvantageously depend on a frame structure.
  • a signal that can be used to calculate the noise power such as a TMCC signal
  • whether or not the noise power calculation method in PTL 2 can be applied depends on the frame structure of a received signal.
  • an object of the present invention is to provide a receiver and the like capable of estimating the reliability information without depending on the received frame structure.
  • a receiver in accordance with one aspect of the present invention is a receiver including: a demodulator that demodulates a modulation wave modulated according to orthogonal frequency division multiplexing (OFDM), the demodulator including: an interference wave detector that detects that a received modulation wave which is received by the receiver includes an interference wave when received power of each sample of the received modulation wave exceeds a threshold, and upon the detection, executes replacement processing of replacing a received signal exceeding the threshold with a predetermined value; a first interference wave power estimation unit configured to estimate interference wave power included in an OFDM symbol included in the received modulation wave on the basis of the number of samples that have been subjected to the replacement processing in the OFDM symbol; and a demodulated data generator that demodulates the received modulation wave by executing demodulation processing of demodulating the received modulation wave that has been subjected to the replacement processing by the interference wave detector on the basis of the interference wave power estimated by the first interference wave power estimation unit, to generate demodul
  • OFDM orthogonal frequency division multiple
  • the interference power can be calculated without depending on the received frame structure, thereby enabling stable reception.
  • FIG. 1 A block diagram showing a configuration of a receiver in accordance with First embodiment.
  • FIG. 2 A block diagram showing a configuration of a demodulator 11 in accordance with First embodiment.
  • FIG. 3A A block diagram showing a configuration of an interference wave detector 102 in accordance with First embodiment.
  • FIG. 3B A view showing an example of an interference wave detection signal.
  • FIG. 4 A block diagram showing a configuration of a time axis processor 103 in accordance with First embodiment.
  • FIG. 5 A block diagram showing a configuration of an interference wave power estimation unit 104 in accordance with First embodiment.
  • FIG. 6 A block diagram showing a configuration of a reliability estimation unit 108 in accordance with First embodiment.
  • FIG. 7 A block diagram showing a configuration of a receiver in accordance with Second embodiment.
  • FIG. 8 A block diagram showing a configuration of a demodulator 21 in accordance with Second embodiment.
  • FIG. 9 A block diagram showing a configuration of an interference wave detector 202 in accordance with Second embodiment.
  • FIG. 10 A block diagram showing a configuration of an interference wave power estimation unit 204 in accordance with Second embodiment.
  • FIG. 11 A block diagram showing a configuration of a receiver in accordance with Third embodiment.
  • FIG. 12 A block diagram showing a configuration of a demodulator 31 in accordance with Third embodiment.
  • FIG. 13 A block diagram showing a configuration of an interference wave power estimation unit 304 in accordance with Third embodiment.
  • FIG. 14A A schematic view showing a transition of CNR in interpolation processing in channel estimation.
  • FIG. 14B A block diagram showing an example of a configuration of a channel estimation unit 106 .
  • FIG. 15 A block diagram showing a configuration of a receiver in accordance with Fourth embodiment.
  • FIG. 16 A block diagram showing a configuration of a demodulator 41 in accordance with Fourth embodiment.
  • FIG. 17 A block diagram showing a configuration of a reliability estimation unit 408 in accordance with Fourth embodiment.
  • FIG. 18 A schematic view illustrating a structure of a DVB-T2 frame in a DVB-T2 scheme.
  • FIG. 19 A view illustrating relationship between FFT size and the number of P2 symbols.
  • FIG. 20 A schematic view illustrating a transmission format (carrier arrangement) in the DVB-T2 scheme.
  • FIG. 21 A schematic view illustrating definition of a carrier interval of SP signals and a symbol interval.
  • FIG. 22 A view illustrating the carrier interval and the symbol interval in each pilot (SP) pattern.
  • FIG. 23 A view illustrating the FFT size, used CP groups, and values used in a modulo operation.
  • FIG. 24 A view illustrating values of the CP groups (CP_g 1 , CP_g 2 , CP_g 3 ) for the pilot patterns.
  • FIG. 25 A view illustrating values of the CP group (CP_g 4 ) for the pilot patterns.
  • FIG. 26 A view illustrating values of the CP group (CP_g 5 ) for the pilot patterns.
  • FIG. 27 A view illustrating values of the CP group (CP_g 6 ) for the pilot patterns.
  • FIG. 28 A view illustrating CP carrier positions added in an Extended mode.
  • FIG. 29 A schematic view illustrating arrangement of pilot signals in each symbol.
  • FIG. 30 A schematic view illustrating a general DVB-T2 receiver.
  • the OFDM technology is a method of transmitting a plurality of narrowband digital modulated signals on multiple frequencies by using a plurality of subcarriers orthogonal to each other, which is excellent in frequency use efficiency.
  • one symbol section is composed of an effective symbol section and a guard interval section, for the periodicity in the symbol, some signals in the effective symbol section are copied and inserted into the guard interval section. This can reduce the effect of interference between symbols, which is caused by multipath interference, and has an excellent resistance to the multipath interference.
  • FIG. 18 shows a structure of a DVB-T2 frame in the DVB-T2 scheme.
  • the DVB-T2 frame is composed of P1 symbols, P2 symbols, and data symbols.
  • FFT Fast Fourier Transform
  • the P2 symbol has the same FFT size as the data symbol, and pilots are inserted into the P2 symbol at regular intervals.
  • the P2 pilot exists every six subcarriers.
  • the P2 pilot exists every three subcarriers. All transmission parameter information necessary for reception, such as a pilot pattern of the data symbols and a carrier extended mode (Extended mode or Normal), the number of symbols in each frame, and modulation method, is added to the P2 symbol. As shown in a table T 190 in FIG. 19 , the number of P2 symbols is set for each FFT size of the P2 symbols.
  • FIG. 20 shows a transmission format of the DVB-T2 scheme.
  • a horizontal axis represents an OFDM carrier (frequency) direction
  • a vertical axis represents an OFDM symbol (time) direction.
  • an SP Spcattered Pilot
  • CP Continuous Pilot
  • FIG. 20 shows a transmission format of the DVB-T2 scheme.
  • a horizontal axis represents an OFDM carrier (frequency) direction
  • a vertical axis represents an OFDM symbol (time) direction.
  • an SP Spcattered Pilot
  • CP Continuous Pilot
  • a carrier interval and a symbol interval of carrier positions where the SP signals exist are Dx and Dy, respectively
  • the insertion interval Dy in the symbol direction and an insertion interval (Dx ⁇ Dy) in the carrier direction, according to each of the SP patterns PP1 to PP8 are shown in a table T 220 in FIG. 22 .
  • the subcarrier position where the CP signals are inserted is determined depending on the FFT size and the SP patterns.
  • FIG. 23 shows which of groups CP_g 1 to CP_g 6 shown in FIG. 24 to FIG. 28 is used according to the FFT size.
  • Values obtained by applying a modulo operation (residue operation) to values shown in FIG. 24 to FIG. 27 by using K_mod in FIG. 23 represent effective subcarrier numbers in which the CP signals exist.
  • the FFT size is 32 k
  • the modulo operation is not performed, and the values shown in FIG. 24 to FIG. 27 become the effective subcarrier numbers in which the CP signals exist as they are.
  • the effective subcarrier numbers shown in FIG. 28 are added. The values in FIG. 28 does not need to be subjected to the modulo operation.
  • FIG. 29 is a schematic view showing a transmission format including the P2 symbols and the Frame Close symbol. As shown in FIG. 29 , more pilots are inserted into the Frame Close (FC) symbol than pilots inserted into the normal data symbol.
  • FC Frame Close
  • FC Framework Close
  • the FC pilots are added and no CP signal exists. Also in the P2 symbols, since a lot of P2 pilots exist, no CP signal exists.
  • FIG. 30 shows an example of a schematic block diagram of an integrated structure according to conventional DVB-T2.
  • the reception structure according to the conventional DVB-T2 scheme includes an A/D converter 1002 , a time axis processor 1003 , an FFT unit 1004 , a channel estimation unit 1005 , an equalizer 1006 , an error correction unit 1007 , and a reliability estimation unit 1008 .
  • the A/D converter 1002 decodes the P1 symbol from an A/D (analog-digital) converted signal.
  • the time axis processor 1003 synchronizes carrier frequencies and sampling frequencies of the P2 symbol and the data symbol.
  • the FFT unit 1004 performs FFT for conversion into a signal along the frequency axis.
  • the channel estimation unit 1005 estimates channel characteristics on the basis of the SP signal included in the signal that has been subjected to FFT.
  • the equalizer 1006 performs distortion compensation (equalization) of the signal that has been subjected to FFT.
  • the error correction unit 1007 performs error correction to decode data.
  • the reliability estimation unit 1008 estimates the reliability information in channel estimation.
  • the estimated reliability information is used for the error correction in the error correction unit 1007 .
  • the DVB-T2 employs an LDPC (Low Density Parity Check) code as an error correction code.
  • LDPC Low Density Parity Check
  • the reliability information representing the reliability of data is necessary for weighting of log likelihood ratio.
  • the reliability information is estimated based on signal power estimated in each symbol and noise power including the effect of thermal noise or interference wave. To improve the error correction performance in LDPC decoding, it is critically important to appropriately generate an integrated propagation state as the reliability information.
  • PTL discloses a method of assessing the noise power existing in each symbol, which is necessary for estimating the reliability information.
  • the reception quality is assessed using at least either TMCC (Transmission Multiplexing Configuration Control) signals or AC (Auxiliary Channel) signals that are successively inserted into predetermined subcarriers in the time direction.
  • TMCC Transmission Multiplexing Configuration Control
  • AC auxiliary Channel
  • the reception quality is calculated from an error between signals obtained by equalizing the TMCC signals by use of the channel characteristics acquired from interpolation of the channel characteristics of the SP signals, and signals obtained by differential decoding and hard decision of the TMCC signals.
  • An impulse interference environment is one of reception environments in which the state of the reception channel is hard to be reflected on the reliability information.
  • the impulse interference is an irregular and random interference signal, and occurs in an impulse manner from power-ON/OFF of household electrical appliances, lighting equipment, or automobile ignition.
  • the impulse interference is diffused into a wider frequency band by the FFT, thereby degrading the reception performance.
  • the noise power locally increases in the symbol in which the interference wave exists. For this reason, when the noise power is averaged among the symbols for improving the accuracy of the noise power of the reliability information, in the symbol in which the impulse interference exists, an error occurs between the reliability information and the actual transmission environment.
  • the reception performance is improved by eliminating a signal having an integrated level higher than a predetermined level.
  • the impulse interference signal since an impulse interference component having a high reception level is eliminated, the impulse interference signal itself does not exist.
  • the desired OFDM signal itself also disappears by eliminating the received signal to disappear, while a noise component generated with the elimination still remains.
  • an error occurs between the reliability information obtained by equalizing the noise power among the symbols and the noise power in the symbol including the noise component remaining with the elimination, resulting in that the LDPC decoding performance cannot be used to the fullest extent.
  • PTL 1 describes an effective method of eliminating such local difference in the reliability information of the symbols to improve the accuracy.
  • average noise power in a symbol direction is compared with noise power in each symbol, and in the case where the noise power in each symbol exceeds a predetermined threshold, it is determined that impulse interference exists, and a value of the noise power in each symbol is used to generate the reliability information.
  • the noise power in each symbol does not exceed the predetermined threshold, it is determined that the impulse interference does not exist, and a value of the averaged noise power in the symbol direction is used to generate the reliability information.
  • PTL 1 fails to disclose a specific method of calculating the noise power in units of symbol.
  • the noise power of the frame including the CP signals can be calculated.
  • the CP signals are not arranged in the P2 symbol and the Frame Close symbol. In such symbols including no CP signal, the noise power cannot be calculated based on the CP signals and therefore, the average noise power in the symbol direction needs to be used in these symbols.
  • a receiver is a receiver including: a demodulator that demodulates a modulation wave modulated according to orthogonal frequency division multiplexing (OFDM), the demodulator including: an interference wave detector that detects that a received modulation wave which is received by the receiver includes an interference wave when received power of each sample of the received modulation wave exceeds a threshold, and upon the detection, executes replacement processing of replacing a received signal exceeding the threshold with a predetermined value; a first interference wave power estimation unit configured to estimate interference wave power included in an OFDM symbol included in the received modulation wave on the basis of the number of samples that have been subjected to the replacement processing in the OFDM symbol; and a demodulated data generator that demodulates the received modulation wave by executing demodulation processing of demodulating the received modulation wave that has been subjected to the replacement processing by the interference wave detector on the basis of the interference wave power estimated by the first interference wave power estimation unit, to generate demodulation data.
  • OFDM orthogonal frequency division multiplexing
  • the receiver calculates the interference wave power included in the OFDM symbol on the basis of the number of samples in which the received power exceeds the predetermined threshold in the OFDM symbol, thereby enabling estimation of the interference wave power in units of the OFDM symbol without depending on the type of signal transmitted in the OFDM symbol.
  • the interference wave power calculated on the basis of the number of samples in which the received power exceeds the predetermined threshold can be used as the interference wave power of the OFDM symbol including no CP signal, even when impulse interference or signal elimination exists in the OFDM symbol including no CP signal, stable reception can be achieved.
  • the interference wave power of the OFDM symbol including particular signals can be estimated by using the particular signals.
  • the interference wave power in units of OFDM symbol can be estimated without depending on the type of signal transmitted in the OFDM symbol.
  • the demodulated data generator may include a reliability estimation unit configured to estimate reliability information with respect to the received modulation wave to obtain a lower reliability of the OFDM symbol as the interference wave power estimated by the first interference wave power estimation unit is larger; and an error correction unit configured to execute error correction processing of correcting an error included in the received modulation wave on the basis of the reliability information estimated by the reliability estimation unit, as the demodulation processing for the received modulation wave, to generate the demodulation data for the received modulation wave.
  • a reliability estimation unit configured to estimate reliability information with respect to the received modulation wave to obtain a lower reliability of the OFDM symbol as the interference wave power estimated by the first interference wave power estimation unit is larger
  • an error correction unit configured to execute error correction processing of correcting an error included in the received modulation wave on the basis of the reliability information estimated by the reliability estimation unit, as the demodulation processing for the received modulation wave, to generate the demodulation data for the received modulation wave.
  • noise power taking into account the estimated interference power can be estimated.
  • error correction can be performed based on the high-accuracy reliability information, thereby enabling stable reception.
  • the error correction unit may be configured to execute weighting processing of a log likelihood ratio in LDPC (Low Density Parity Check) demodulation on the basis of the reliability information estimated by the reliability estimation unit, as the demodulation processing for the received modulation wave, to generate demodulation data for the received modulation wave.
  • LDPC Low Density Parity Check
  • the LDPC (Low Density Parity Check) demodulation processing can be executed based on the high-accuracy reliability information.
  • the inputted reliability information can be taken into account, and by inputting the high-accuracy reliability information, higher-accuracy demodulation processing can be achieved.
  • the demodulated data generator may include: an FFT (Fast Fourier Transform) window position detector that identifies a start timing of the OFDM symbol included in the received modulation wave; and an FFT unit configured to apply FFT processing to the received modulation wave on the basis of the start timing of the OFDM symbol, which is identified by the FFT window position detector, and applies the demodulation processing to the received modulation wave that has been subjected to the FFT processing, to generate the demodulation data.
  • FFT Fast Fourier Transform
  • impulse interference or signal elimination that exists during the actually Fourier-transformed symbol period can be estimated.
  • the interference wave detector may execute, as the replacement processing, processing of replacing the received signal exceeding the threshold with 0 as the predetermined value.
  • the interference wave detector may execute processing of replacing the received signal exceeding the threshold with the threshold as the predetermined value.
  • the demodulator further may include a second interference wave power estimation unit configured to estimate interference wave power included in a first OFDM symbol included in the received modulation wave on the basis of interference wave power included in a second OFDM symbol that is different from the first OFDM symbol and magnitude of an effect on the first OFDM symbol, which is brought by the interference wave power included in the second OFDM symbol
  • the demodulated data generator applies demodulation processing including error correction taking into account the interference wave power estimated by the first interference wave power estimation unit to a first OFDM symbol group having at least one OFDM symbol included in the received modulation wave to generate demodulation data for the received modulation wave
  • demodulation processing including error correction taking into account the interference wave power estimated by the second interference wave power estimation unit to a second OFDM symbol group having an OFDM symbol that is the OFDM symbol included in the received modulation wave other than the OFDM symbol of the first OFDM symbol group, to generate the demodulation data for the received modulation wave.
  • the interference wave power can be calculated according to the proper interference wave power method selected from the plurality of interference wave power estimation methods for each symbol, and the calculated interference wave power can be used in the demodulation processing to achieve effective demodulation, thereby enabling stable reception.
  • the receiver may receive an airwave based on a Digital Video Broadcasting-Terrestrial 2 (DVB-T2) scheme as the modulation wave, and the demodulated data generator may use an OFDM symbol group including no OFDM symbol having a CP (Continual Pilot) signal as the first OFDM symbol group, to generate the demodulation data for the received modulation wave.
  • DVD-T2 Digital Video Broadcasting-Terrestrial 2
  • CP Continuous Pilot
  • the interference power can be calculated in even the symbol, to which the processing using the CP signals can be applied, and the calculated interference power can be used in the demodulation processing to achieve effective demodulation, thereby enabling stable reception.
  • the demodulated data generator may use an OFDM symbol group including an OFDM symbol having a P2 symbol or an FC (Frame Close) symbol according to the DVB-T2 scheme as the first OFDM symbol group, to generate the demodulation data for the received modulation wave.
  • an OFDM symbol group including an OFDM symbol having a P2 symbol or an FC (Frame Close) symbol according to the DVB-T2 scheme as the first OFDM symbol group, to generate the demodulation data for the received modulation wave.
  • the interference power can be calculated in even the P2 symbol or the FC symbol, to which the processing using the CP signals can be applied, and the calculated interference power can be used in the demodulation processing to achieve effective demodulation, thereby enabling stable reception.
  • the demodulated data generator may further include a channel estimation unit configured to estimate channel characteristics of the modulation wave on the basis of the interference wave power estimated by the first interference wave power estimation unit, and the demodulated data generator may demodulate the received modulation wave by executing demodulation processing based on the channel characteristicss estimated by the channel estimation unit, to generate the demodulation data.
  • a channel estimation unit configured to estimate channel characteristics of the modulation wave on the basis of the interference wave power estimated by the first interference wave power estimation unit
  • the demodulated data generator may demodulate the received modulation wave by executing demodulation processing based on the channel characteristicss estimated by the channel estimation unit, to generate the demodulation data.
  • the interference power can be calculated whether or not noise in the symbol can be estimated, and the calculated interference power can be used to achieve effective channel estimation, thereby enabling stable reception.
  • the channel estimation unit may include a plurality of different channel estimation interpolation units that perform mutually different methods of interpolating the channel characteristicss
  • the first interference wave power estimation unit may be configured to estimate interference power corresponding to each of the channel estimation interpolation units
  • the channel estimation unit may be configured to output one of outputs from the plurality of channel estimation interpolation units as the channel characteristicss on the basis of the interference power estimated by the first interference wave power estimation unit.
  • the interference power can be calculated whether or not noise in the symbol can be estimated, and the calculated interference power can be used to achieve effective channel estimation, thereby enabling stable reception.
  • the first interference wave power estimation unit may be configured to calculate interference wave power included in the OFDM symbol included in the received modulation wave, using the number of samples that have been subjected to the replacement processing in the OFDM symbol, the number of FFT samples in the OFDM symbol, and a predetermined coefficient.
  • the interference power can be calculated based on the number of samples exceeding the predetermined threshold during the OFDM symbol period, the number of FFT samples, and the predetermined coefficient with high accuracy, and the calculated interference power can be used to achieve effective demodulation, thereby enabling stable reception.
  • the demodulated data generator may further include a channel estimation unit configured to estimate a channel characteristic of each carrier included in a fourth OFDM symbol disposed before or after a third OFDM symbol included in the received modulation wave by interpolation using channel characteristicss calculated using a pilot signal included in the third OFDM symbol, an equalizer configured to execute equalization processing of correcting a signal of the fourth OFDM symbol on the basis of the channel characteristicss estimated by the channel estimation unit, an error correction unit configured to perform error correction for the signal corrected by the equalizer on the basis of reliability information representing reliability of the signal corrected by the equalizer, and a reliability information estimation unit configured to estimate reliability information of the signal included in the fourth OFDM symbol on the basis of interference wave power of the third OFDM symbol, which is estimated by the interference wave power estimation unit.
  • a channel estimation unit configured to estimate a channel characteristic of each carrier included in a fourth OFDM symbol disposed before or after a third OFDM symbol included in the received modulation wave by interpolation using channel characteristicss calculated using a pilot signal included in the third OFDM symbol
  • the interference power can be calculated whether or not noise in the symbol can be estimated, and the calculated interference power can be used to achieve effective channel estimation of other OFDM symbols, thereby enabling stable reception.
  • An integrated circuit is an integrated circuit including a demodulator that demodulates a modulation wave modulated according to orthogonal frequency division multiplexing (OFDM), the demodulator including: an interference wave detector that detects that a received modulation wave that is the modulation wave received by the receiver includes interference wave when received power of each sample of the received modulation wave exceeds a threshold, and upon the detection, executes replacement processing of a replacing received signal exceeding the threshold with a predetermined value; a first interference wave power estimation unit configured to estimate interference wave power included in an OFDM symbol included in the received modulation wave on the basis of the number of samples that have been subjected to the replacement processing; and a demodulated data generator that demodulates the received modulation wave by executing demodulation processing of demodulating the received modulation wave that has been subjected to the replacement processing by the interference wave detector on the basis of the interference wave power estimated by the first interference wave power estimation unit, to generate demodulation data.
  • OFDM orthogonal frequency division multiplexing
  • the integrated circuit has the same effect as the above-mentioned receiver.
  • a receiving method is a receiving method comprising demodulating a modulation wave modulated according to orthogonal frequency division multiplexing (OFDM), wherein the demodulating includes: an interference wave detection step of detecting that received modulation wave that is the modulation wave received according to the receiving method includes interference wave when received power of each sample of the received modulation wave exceeds a threshold, and upon the detection, executing replacement processing of replacing a received signal exceeding the threshold with a predetermined value; a first interference wave power estimation step of estimating interference wave power included in an OFDM symbol included in the received modulation wave on the basis of the number of samples that have been subjected to the replacement processing; and a demodulation data generation step of demodulating the received modulation wave by executing demodulation processing of demodulating the received modulation wave that has been subjected to the replacement processing in the detecting on the basis of the interference wave power estimated in the estimating, to generate demodulation data.
  • OFDM orthogonal frequency division multiplexing
  • the receiving method has the same effect as the above-mentioned receiver.
  • a program as one aspect of the present invention causes a computer to perform the above-mentioned receiving method.
  • the program has the same effect as the above-mentioned receiver.
  • FIG. 1 is a block diagram showing a receiver 10 in First embodiment of the present invention.
  • the receiver 10 includes an antenna 1 , a tuner 2 , a demodulator 11 , a decoder 3 , and a display 4 .
  • the antenna 1 receives a modulation wave modulated according to orthogonal frequency division multiplexing (OFDM).
  • OFDM orthogonal frequency division multiplexing
  • the tuner 2 selects a received signal of a desired reception channel from the modulation wave received by the antenna 1 .
  • the demodulator 11 demodulates the received analog signal selected by the tuner 2 .
  • the decoder 3 decodes the signal that is demodulated by the demodulator 11 and compressed according to the H.264 or the like.
  • the display 4 outputs video/voice decoded by the decoder 3 .
  • FIG. 2 is a block diagram showing a configuration of the demodulator 11 in accordance with First embodiment.
  • the demodulator 11 includes an A/D converter 101 , an interference wave detector 102 , an interference wave power estimation unit 104 , and a demodulated data generator 12 .
  • the demodulated data generator 12 includes a time axis processor 103 , an FFT unit 105 , a channel estimation unit 106 , equalizer 107 , reliability estimation unit 108 , and an error correction unit 109 .
  • the A/D converter 101 converts the analog output signal from the tuner 2 into a digital signal, and outputs the digital signal to the interference wave detector 102 .
  • the interference wave detector 102 detects an interference wave contained in the received signal converted into the digital signal by the A/D converter 101 and outputs a detection result to the interference wave power estimation unit 104 as well as converts the received signal (sample) containing the detected interference wave into a predetermined value and outputs the predetermined value to the time axis processor 103 . Specific processing will be described later.
  • the time axis processor 103 determines a start time position of FFT processing during the OFDM symbol period (hereinafter referred to as FFT window position) for the output signal of the interference wave detector 102 , outputs the start time position to the FFT unit 105 , and outputs the FFT window position information to the interference wave power estimation unit 104 .
  • FFT window position a start time position of FFT processing during the OFDM symbol period
  • the interference wave power estimation unit 104 estimates interference power on the basis of the received signal that has been subjected to the interference wave processing by the interference wave detector 102 and the FFT window position information determined by the time axis processor 103 .
  • the interference wave power estimation unit 104 corresponds to the first interference wave power estimation unit. Specific processing performed by the interference wave power estimation unit 104 will be described later.
  • the FFT unit 105 Fourier-transforms the output signal from the time axis processor 103 into a signal along the frequency axis on the basis of an FFT window position signal, and outputs the Fourier-transformed signal to the channel estimation unit 106 and the equalizer 107 .
  • the channel estimation unit 106 interpolates channel characteristics obtained by dividing the SP signals contained in the signal Fourier-transformed according to FFT by known SP signals, thereby estimating the channel characteristicss in all subcarriers, and outputs the estimated channel characteristics to the equalizer 107 and the reliability estimation unit 108 .
  • the equalizer 107 corrects phase and amplitude distortion of the output signal from the FFT unit 105 , which is generated in the channel, on the basis of the channel characteristics estimated by the channel estimation unit 106 .
  • the reliability estimation unit 108 finds the noise power on the basis of a channel estimated value estimated by the channel estimation unit 106 and the interference power estimated by the interference wave power estimation unit 104 , and generates reliability information to be used in the error correction unit 109 from the noise power.
  • the error correction unit 109 corrects an error of the signal corrected by the equalizer 107 on the basis of the reliability information estimated by the reliability estimation unit 108 .
  • FIG. 3A is a view showing a configuration of the interference wave detector 102 .
  • FIG. 3B shows an example of an interference wave detection signal.
  • the interference wave detector 102 includes an interference wave sample detector 111 and a mask processor 112 .
  • the interference wave sample detector 111 compares the received signal ((a) in FIG. 3B ) converted into the digital signal by the A/D converter 101 with a predetermined threshold, generates a signal representing a sample position exceeding the threshold value, and outputs the signal representing the sample position together with the received signal to the mask processor 112 .
  • the mask processor 112 replaces the received signal with 0 ((c) in FIG. 3B ), and outputs 0 together with the interference wave detection signal to the time axis processor 103 and the interference wave power estimation unit 104 .
  • FIG. 4 shows a configuration of the time axis processor 103 .
  • the time axis processor 103 includes a synchronizer 121 and an FFT window position detector 122 .
  • the synchronizer 121 frequency-converts an output signal from the interference wave detector 102 into a baseband signal, synchronizes the carrier frequency with the sampling frequency, and outputs the baseband signal to the FFT window position detector 122 .
  • the FFT window position detector 122 determines the FFT window position of the OFDM symbol, and outputs the FFT window position to the FFT unit 105 and the interference wave power estimation unit 104 .
  • FIG. 5 shows a configuration of the interference wave power estimation unit 104 .
  • the interference wave power estimation unit 104 includes an interference wave sample counter 131 and an interference power converter 132 .
  • the interference wave sample counter 131 outputs the number of samples determined as “interference wave exists” in the OFDM symbol section during which the FFT processing is executed, by using the FFT window position information detected by the FFT window position detector 122 , to the interference power converter 132 .
  • the interference power converter 132 uses the number of samples of “interference wave exists” in the OFDM symbol section, which is counted by the interference wave sample counter 131 , the interference power converter 132 estimates interference power existing in the OFDM symbol, and outputs the estimated interference power to the reliability estimation unit 108 . Detailed operations of each unit will be sequentially described.
  • the interference power converter 132 estimates the noise amount increased in each OFDM symbol according to the conversion formula (Equation 1), and outputs the estimated noise amount to the reliability estimation unit 108 , thereby increasing the accuracy of the reliability information to improve the reception performance.
  • FIG. 6 is a view showing a configuration of the reliability estimation unit 108 .
  • the reliability estimation unit 108 shown in FIG. 6 includes a noise estimation unit 141 , an interference power adder 142 , and a reliability information converter 143 .
  • the noise estimation unit 141 estimates an average noise power value among the OFDM symbols (average noise power among the symbols) on the basis of the received CP signal.
  • the interference power adder 142 adds the interference power estimated by the interference wave power estimation unit 104 to the estimated average noise power value among the symbols, and outputs the noise power for each symbol taking into account the effect of the interference wave.
  • the reliability information converter 143 estimates the reliability information to be used for LDPC decoding on the basis of the OFDM signal power based on the channel characteristics, which is estimated by the channel estimation unit 106 , and the noise power calculated by the interference power adder 142 , and outputs the reliability information to the error correction unit 109 to achieve effective error correction.
  • noise estimation unit 141 To estimate noise in the noise estimation unit 141 , for example, the configuration described in PTL 1, in which the TMCC signals are replaced with the CP signals, is adopted. Specifically, a known CP signal X CP is compared with a received signal Y CP equalized using the channel characteristics H CP obtained through channel estimation by interpolation of the SP signals, and uses its error amount as the noise power of the CP signals representing the noise amount of the OFDM symbol. Since the noise amount is calculated from some signals (CP signals), to improve the estimation accuracy with respect to thermal noise component, average noise power among symbols N Acc accumulated over some symbols is used.
  • the interference wave power estimation unit 104 may also process sample timing of the interference wave detection signal. Further, based on a signal after rate conversion, the interference detection and processing of the interference detection sample by the interference wave detector 102 (processing of converting into 0) may be performed. In this case, an interference detection signal need not allow for the effect of rate conversion.
  • the mask processor 112 replaces the received signal with 0 on the basis of the signal detected by the interference wave sample detector 111 in this embodiment, batch processing may be performed such that the sample exceeding the threshold is replaced with 0 to output a detection signal.
  • the reliability information converter 143 may convert the reliability information by using information other than the noise power and the signal power. For example, by using a frequency-varying component that occurs with the Doppler frequency, the reliability information corresponding to frequency variance can be estimated.
  • the number of samples included in the OFDM symbol which is calculated by the interference wave sample counter 131 , represents the noise amount locally increased by eliminating the OFDM signal in the symbol. For this reason, the number of interference wave samples may be used as a signal representing that the interference wave exists in various blocks. For example, in the calculation of the average noise amount among symbols in the noise estimation unit 141 , the noise amount of the symbol exceeding the predetermined number of interference wave samples may be eliminated in averaging processing.
  • one aspect of the present invention is applied to the error correction method or demodulation method using the LDPC in this embodiment, it can be applied to other error correction methods or demodulation methods.
  • the receiver in accordance with one aspect of the present invention can calculate the interference wave power in the OFDM symbol on the basis of the number of samples having the received power exceeding the predetermined threshold in the OFDM symbol, thereby estimating the interference wave power in units of OFDM symbol without depending on the type of the signal transmitted in the OFDM symbol.
  • the interference wave power calculated based on the number of samples having the received power exceeding the predetermined threshold can be used as the interference wave power of the OFDM symbol including no CP signal.
  • the interference wave power of the OFDM symbol including particular signals can be estimated by using the particular signals.
  • the interference wave power can be estimated in the units of OFDM symbol without depending on the type of signal transmitted in the OFDM symbol.
  • the noise power taking into account the estimated interference power can be estimated to generate the reliability information. Therefore, even when impulse interference or signal elimination exists, error correction can be performed based on the high-accuracy reliability information, thereby enabling stable reception.
  • the LDPC (Low Density Parity Check) demodulation processing can be performed on the basis of the high-accuracy reliability information.
  • LDPC demodulation processing enables demodulation processing taking into account the inputted reliability information, and realizes demodulation processing with higher accuracy by inputting the high-accuracy reliability information.
  • the interference power can be calculated whether or not noise in the symbol can be estimated. Then, effective channel estimation can be achieved based on the calculated interference power, thereby enabling stable reception.
  • the interference power can be calculated with high accuracy, and effective demodulation can be achieved on the basis of the calculated interference power, thereby enabling stable reception.
  • a receiver in accordance with Second embodiment of the present invention will be described below with reference to FIG. 7 to FIG. 10 .
  • the same components as those in FIG. 1 to FIG. 6 are given the same reference numerals and description thereof is omitted.
  • FIG. 7 is a block diagram showing a receiver 20 in accordance with Second embodiment of the present invention
  • FIG. 8 is a block diagram showing a configuration of a demodulator 21 .
  • FIG. 8 is different from FIG. 2 only in an interference wave detector 202 and an interference wave power estimation unit 204 .
  • FIG. 9 is a view showing a configuration of the interference wave detector 202 .
  • the interference wave detector 202 includes an interference wave sample detector 211 and a clip processor 212 .
  • the interference wave sample detector 211 compares a received signal converted into a digital signal by an A/D converter with a predetermined threshold, and outputs an interference wave detection signal together with the received signal.
  • the clip processor 212 replaces the received signal with a predetermined value.
  • the predetermined value may be the same as the threshold in the interference wave sample detector 211 .
  • the predetermined value may be same as the negative threshold in this processing.
  • the interference wave detector 202 outputs the interference wave detection signal to the interference wave power estimation unit 204 .
  • FIG. 10 is a block diagram showing a configuration of the interference wave power estimation unit 204 .
  • the interference wave power estimation unit 204 includes an interference wave sample counter 131 and an interference power converter 232 .
  • the interference wave sample counter 131 counts the number of samples determined as “interference wave exists”, which are included in the OFDM symbol, and outputs the count to the interference power converter 232 .
  • the interference power converter 232 calculates the interference wave power included in the OFDM signal.
  • the interference wave is converted into the predetermined value (clip processing)
  • clip processing since the interference wave is converted into the predetermined value (clip processing), it can be deemed that the interference wave corresponding to the predetermined value for the number of interference wave samples exists in the OFDM symbol.
  • the OFDM signal power is P OFDM and the square of the interference wave clipped value is A Clip ⁇ P OFDM
  • the signal level of each sample of the OFDM signal becomes P OFDM /N FFT
  • the signal level of the clipped interference wave power becomes A Clip ⁇ P OFDM /N FFT . Consequently, interference wave power I Clip at clipping of the interference wave can be expressed by (Equation 2).
  • I Clip N I ⁇ A Clip ⁇ P OFDM /N FFT (Equation 2)
  • the interference power adder 142 of the reliability estimation unit 108 takes into account the interference wave component included in the symbol to increase the accuracy of the reliability information to be used for LDPC decoding in the reliability estimation unit, thereby enabling stable reception.
  • the interference wave power estimation unit 104 may also process sample timing of the interference wave detection signal. Further, based on a signal after rate conversion, the interference detection and processing of the interference detection sample by the interference wave detector 202 (processing of converting into the predetermined value) may be performed. In this case, an interference detection signal need not allow for the effect of rate conversion.
  • the clip processor 212 performs conversion into the predetermined value on the basis of the signal detected by the interference wave sample detector 211 , batch processing may be performed such that the sample exceeding the threshold is replaced with the predetermined value to output a detection signal.
  • the OFDM signal component may be subtracted.
  • a receiver in accordance with Third embodiment of the present invention will be described below with reference to FIG. 11 to FIG. 14A .
  • the same components as those in FIG. 1 to FIG. 6 are given the same reference numerals and description thereof is omitted.
  • FIG. 11 is a block diagram showing a receiver 30 in accordance with Third embodiment of the present invention
  • FIG. 12 is a block diagram showing a configuration of a demodulator 31 .
  • the demodulator 31 shown in FIG. 12 is different from the demodulator 11 in First embodiment in a configuration of an interference wave power estimation unit 304 .
  • FIG. 13 is a view showing the configuration of the interference wave power estimation unit 304 .
  • the interference wave power estimation unit 304 includes an interference wave sample counter 131 , an interference power converter 132 , a second interference power converter 332 , and an adder 333 .
  • the interference wave power estimation unit 304 corresponds to a second interference wave power estimation unit.
  • the interference wave sample counter 131 counts the number of samples determined as “interference wave exists” in the OFDM symbol on the basis of the interference wave detection signal detected by the interference wave detector 102 and the OFDM symbol position detected by the FFT window position detector 122 , at which the FFT is performed, and outputs the count to the interference power converter 132 and the second interference power converter 332 .
  • the interference power converter 132 calculates the interference power included in the received OFDM symbol from the output of the interference wave sample counter 131 .
  • This embodiment is different from First embodiment in the second interference power converter 332 .
  • the second interference power converter 332 calculates the interference power occurring in the current OFDM symbol from the interference wave including other OFDM symbols.
  • the interference wave power is estimated by the channel estimation.
  • the adder 333 adds the interference power of the current OFDM symbol estimated by the interference power converter 132 and the interference power of the other OFDM symbols estimated by the second interference power converter 332 and outputs the sum.
  • Estimation of the channel characteristics is to obtain the channel characteristicss of all subcarriers by interpolating the channel characteristicss of the SP signals, the P2 pilot signals, and the FC signals that exist in a distributed manner in the time axis (symbol) direction and the frequency axis (carrier) direction.
  • Interpolation methods include (A) a method of interpolating the signals in the time axis (symbol) direction and then, interpolating the signals in the frequency axis (carrier) direction, and (B) a method of interpolating the signals only in the frequency axis (carrier) direction.
  • FIG. 14A shows a transition of CNR (Carrier to Noise ratio) of each OFDM symbol corrected by the equalizer 107 in each of cases where as the interpolation processing in the channel estimation in an impulse interference environment, (A) time axis interpolation and frequency interpolation are used, and (B) only the frequency axis interpolation is used (no time axis interpolation).
  • a horizontal axis represents the symbol direction (time direction), and a vertical axis represents the CNR.
  • the second interference power converter 332 takes into account of the effect of the interference wave in the channel estimation, and in the case of (B) only the frequency axis interpolation, the effect of the current symbol on the channel characteristics is regarded as the interference power.
  • the effect of the symbol having interference and the symbols before and after the current symbol is also regarded as the interference power.
  • the number of interference wave samples, which is outputted from the interference wave sample counter 131 is subjected to the same processing as time interpolation, the number of interference samples that takes into account the effect of the interference wave by time axis interpolation is estimated, and the interference power including the interpolation error is calculated.
  • the effect of the interference wave on the channel estimation changes depending on the patterns (A) time axis interpolation+frequency axis interpolation, and (B) only frequency axis interpolation. Details of each pattern will be described below.
  • the DVB-T2 scheme has eight types of SP patterns.
  • linear interpolation in the time axis direction is used as an example.
  • An SP carrier interval in the time axis direction is classified into two types: (1) every two carriers and (2) every four carriers.
  • the range in which the effect of the interference wave in the time interpolation is spread is one symbol in the case (1) and three symbols in the case (2) before and after the symbol having the detected interference wave.
  • the number of interference wave samples for estimating the channel estimation error in the i symbol due to the interference wave: (1) N H — TF2sym and (2) N H — TF4sym are as follows.
  • N H ⁇ ⁇ _ ⁇ ⁇ TF ⁇ ⁇ 2 ⁇ sym ⁇ ( i ) 1 / 2 ⁇ ⁇ N I ⁇ ( i ) + ( 1 / 2 ) 2 ⁇ ( N I ⁇ ( i - 1 ) + N I ⁇ ( i + 1 ) ) ⁇ ( Equation ⁇ ⁇ 3 )
  • N H ⁇ ⁇ _ ⁇ ⁇ TF ⁇ ⁇ 4 ⁇ sym ⁇ ( i ) 1 / 4 ⁇ ⁇ N I ⁇ ( i ) + ( 3 / 4 ) 2 ⁇ ( N I ⁇ ( i - 1 ) + N I ⁇ ( i + 1 ) ) + ( 2 / 4 ) 2 ⁇ ( N I ⁇ ( i - 2 ) + N I ⁇ ( i + 2 ) ) + ( 1 / 4 ) 2 ⁇ ( N I ⁇ ( i - 3 ) + N I
  • N H — F (i) N I ( i ) (Equation 5)
  • the interference power taking into account the channel estimation error on the basis of the number of interference wave samples according to each of the above-mentioned interpolation methods it is required to correct the noise amount related to SP signal power and interpolation filter band.
  • the interference power taking into account the channel estimation error in the cases (A) and (B) is as represented by (Equation 6) and (Equation 7), respectively. It is assumed that A SP is boost of the SP signal, BWT is band of the time interpolation filter, and BWF is band of the frequency interpolation filter.
  • the adder 333 adds the interference power estimated by the interference wave power estimation unit to the interference power taking into account the channel estimation error corresponding to respective interpolation method, thereby reflecting the interference power included in the OFDM symbol as well as the interference power including the effect of the interference wave in the channel estimation. Since the interference power can be appropriately reflected on the reliability information in the interference power adder 142 of the reliability estimation unit 108 , high-accuracy reliability information can be obtained, resulting in effective LDPC decoding and improvement of the reception performance.
  • the adder 333 adds the interference power from the interference power converter 132 to the interference power from the second interference power converter 332 in this embodiment, the adder 333 may use the interference power from either of the converters.
  • linear interpolation is adopted as the time axis interpolation, the linear interpolation is not limited to this, and any interpolation method (interpolation coefficient) may be adopted.
  • the interpolation method may be selected based on the calculated interference power.
  • a channel estimation unit 206 shown in FIG. 14B may be used.
  • the channel estimation unit 206 includes a first channel interpolation unit 206 A, a second channel interpolation unit 206 B, and a selector 206 S.
  • the first channel interpolation unit 206 A and the second channel interpolation unit 206 B estimate different channel characteristicss.
  • the selector 206 S selects either an output from the first channel interpolation unit 206 A or an output from the second channel interpolation unit 206 B, as the channel characteristics.
  • the reliability information in the demodulation processing can be selected from a plurality of channel characteristicss. Since one of the outputs from the plurality of channel interpolation units is selected, the interference wave power estimation unit can estimate the interference power corresponding to each interpolation processing.
  • the sample having interference is masked to 0 in this embodiment unlike First embodiment, as in Second embodiment, the sample having interference may be replaced with the predetermined value may be taken into account in (Equation 3) to (Equation 5).
  • the receiver in accordance with one aspect of the present invention can calculate the interference wave power according to the appropriate interference wave power estimation method selected the plurality of interference wave power estimation methods for each symbol to use the interference wave poser in the demodulation processing, and achieve effective decoding by using the interference wave power, thereby enabling stable reception.
  • the interference power of the symbols that cannot be subjected to the processing using the CP signals can be calculated.
  • the demodulation processing can be performed using the calculated interference power to achieve effective demodulation, thereby enabling stable reception.
  • the interference power of the P2 symbol and the FC symbol that cannot be subjected to the processing using the CP signals can be calculated.
  • the demodulation processing can be performed using the calculated interference power to achieve effective demodulation, thereby enabling stable reception.
  • the interference power can be calculated whether or not noise in the symbol can be estimated, and the interpolation method for effective channel estimation can be selected based on the interference power, thereby enabling stable reception.
  • a receiver in accordance with Fourth embodiment of the present invention will be described below.
  • the same components as those in FIG. 1 to FIG. 6 are given the same reference numerals and description thereof is omitted.
  • FIG. 15 is a block diagram showing a receiver 40 in accordance with Fourth embodiment of the present invention
  • FIG. 16 is a block diagram showing a configuration of a demodulator 41 .
  • the demodulator 41 is different from the demodulator 11 in First embodiment in addition of the interference power in a reliability estimation unit 408 .
  • FIG. 17 is a block diagram showing a configuration of the reliability estimation unit 408 .
  • the reliability estimation unit 408 includes a noise estimation unit 441 , an interference power adder 442 , and a reliability information converter 143 .
  • the noise estimation unit 441 outputs an average symbol noise estimated value averaged in the symbol direction together with non-average noise estimated value for each symbol to the interference power adder 442 .
  • the interference power adder 442 is different from the interference power adder 142 in First embodiment in that whether or not the interference power estimated by the interference wave power estimation unit 104 is added is selected according to the symbol to be processed.
  • the average symbol noise estimated value with the addition to the interference power is outputted in the case of a particular symbol, and the non-average noise estimated value for each symbol in the symbol direction without the addition to the interference power is outputted in the case of the symbols other than the particular symbol.
  • a specific example in the DVB-T2 scheme will be described below.
  • the P2 symbol and the FC symbol do not include the CP signal according to the DVB-T2 scheme, in these symbols, noise power cannot be estimated by using the CP signal.
  • noise power can be estimated by using the CP signal for each symbol.
  • the noise estimated value averaged in the symbol direction with the addition to the interference power is outputted.
  • the non-average noise estimated value for each symbol without the addition of the symbol direction is outputted.
  • the noise estimated value calculated for each symbol in the symbols that can estimate noise for each symbol by using the noise estimated value calculated for each symbol in the symbols that can estimate noise for each symbol, and adding the interference power to the average noise estimated value in the symbols that cannot estimate noise, the noise amount can be correctly reflected on the reliability information. For this reason, high-accuracy reliability information can be obtained, resulting in effective LDPC decoding and improvement of the reception performance.
  • the non-average noise estimated value for each symbol in the symbol direction is used.
  • the present invention is not limited to this, and the noise estimated value averaged in the symbol direction or the non-average noise estimated value for each symbol may be selected. For example, these values are compared to each other, and when the noise estimated value for each symbol is larger, the noise estimated value for each symbol may be used, and when the noise estimated value for each symbol is not larger, the average noise estimated value may be used.
  • the noise estimated value for each symbol may be used, and when the number of interference samples is not larger than a predetermined number, the average noise estimated value may be used.
  • the configuration in which the necessity of addition of the interference power is selected according to the type of symbols is applied to First embodiment, the configuration may be applied to Second embodiment and Third embodiment.
  • the receiver in accordance with one aspect of the present invention can calculate the interference power on the basis of the number of samples exceeding the predetermined threshold during the OFDM symbol period, to calculate the interference power whether or not noise can be estimated in the symbol, and can perform effective channel estimation of the other OFDM symbols on the basis of the calculated interference power, thereby enabling stable reception.
  • the reliability of the reliability information of the current symbol may be decreased by a predetermined value from that of the other symbols according to the presence/absence of the interference wave power without estimating details of the interference wave power in (Equation 1) to (Equation 3).
  • the reliability estimated value may be reduced to half. In this case, it is not need to calculate detailed interference power, achieving reduction of circuit size.
  • Each component of the OFDM receivers in accordance with First to Fourth embodiments may be formed of an LSI as an integrated circuit.
  • the components may be individually shaped into one chip, or may be partially or wholly integrated into one chip.
  • LSI is mentioned herein, IC, system LSI, super LSI, or ultra LSI may be called according to integration degree.
  • the integrated circuit is not limited to the LSI, may be realized by a dedicated circuit or a general processor. FPGA (Field Programmable Gate Array) or a reconfigurable processor capable of reconfiguring connection and setting of circuit cells in the LSI can be used.
  • FPGA Field Programmable Gate Array
  • a reconfigurable processor capable of reconfiguring connection and setting of circuit cells in the LSI can be used.
  • the functional blocks may be integrated by use of the new technology. Biotechnology is one of possible technologies.
  • At least a part of the operational procedure of the receivers in First to Fourth embodiments may be written into an integrated program, and for example, a CPU (Central Processing Unit) may read and execute the program stored in a memory, or the program may be stored in a storage medium and then, distributed.
  • a CPU Central Processing Unit
  • the receivers in First to Fourth embodiments may be realized according to a receiving method that executes at least a part of the written reception processing.
  • Any receiver, receiving method, integrated circuit, or program that executes a part of the reception processing realizing First to Fourth embodiments may be combined to realize First to Fourth embodiments.
  • a part of the configuration of the receiver which is described in each of the above-mentioned embodiments, may be realized by the receiver or the integrated circuit, the operational procedure executed by remaining parts of the configuration may be written into the reception program, and for example, the CPU may read and execute the program stored in the memory.
  • the present invention is not limited to this.
  • the present invention can be also applied to the field of OFDM communication that desires improvement of the accuracy of estimating the noise power according to change in the channel due to the interference wave.
  • each component may be configured of dedicated hardware, or realized by executing a software program suitable for each component.
  • a program execution unit such as a CPU or a processor may read and execute a software program stored in a storage medium such as a hard disc or a semiconductor memory to realize each component.
  • a following program is an example of software that realizes an image decoder in each of the above-mentioned embodiments.
  • the program causes a computer to perform a receiving method including demodulating modulation wave modulated according to orthogonal frequency division multiplexing (OFDM), and the demodulation step includes an interference wave detection step of detecting that received modulation wave as the modulation wave received according to the receiving method includes interference wave when received power of each sample of the received modulation wave exceeds a threshold, and upon the detection, executing replacement processing of replacing received signal exceeding the threshold with a predetermined value, a first interference wave power estimation step of estimating interference wave power included in an OFDM symbol included in the received modulation wave on the basis of the number of samples that have been subjected to the replacement processing, and a demodulation data generation step of demodulating the received modulation wave by executing demodulation processing of demodulating the received modulation wave that has been subjected to the replacement processing in the detecting on the basis of the interference wave power estimated in the estimating, to generate demodulation data.
  • OFDM orthogonal frequency division multiplexing
  • the receiver according to the present invention has functions of detecting the presence/absence of the interference wave for each sample in the time axis region, estimating the interference power on the basis of the number of samples having the interference wave during the FFT sample period of the OFDM symbol, and estimating the reliability information used for the LDPC decoding in consideration of the interference power, and is effective for the OFDM receiver such as DVB-T2 requiring high-accuracy reliability information as well as devices in wider fields such as measurement.

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